This invention relates to an electric power converting apparatus for driving a driving motor of a car from a storage battery mounted thereon.
As is well known in the art, in a battery car the DC power of a storage battery is applied directly to a DC driving motor or to an AC driving motor through an inverter which converts direct current into alternating current. In this system all power is supplied from the battery and its capacity and weight are large so that it is necessary to select a reasonable battery. Batteries for use in motor cars generally have a rating of 6 cells and 12 volts.
Since a series connection of batteries is not advantageous, 12 V to 24 V is advantageous for batteries for driving electric motor cars. On the other hand, high voltage is advantageous for the driving motor. For this reason, motor car driving motors generally have a rating of about 10 to 100 KW and 100 to 400 V. In earlier arrangements, the DC voltage of the battery was applied to a DC driving motor, and the battery voltage was selected to be from 48 to 96 V. This system, however, is not satisfactory in view of the operating characteristics and economy. Such an electric car requires a charging facility but as most charging facilities are bulky it is impossible to mount them on the car. Accordingly, the charging facilities are generally installed on the ground. Since a DC motor is not only expensive but also requires troublesome maintenance, a recent trend is the use of an AC motor, particularly an induction motor.